1-Octen-3-ol and 13-hydroperoxylinoleate are products of distinct pathways in the oxidative breakdown of linoleic acid by Pleurotus pulmonarius

Cultivation and Nutritional Evaluation of Agaricus bisporus with Tea Residue as Culture Medium

Different constituents of the cultivation substrate have significant effect on the yield and quality of edible mushrooms. The residue after the extraction of instant tea has exhibited to be biologically significant, and could be used as a substrate for cultivation. This study aimed to investigate the feasibility of tea extraction residue (TER) on button mushroom (Agaricus bisporus) cultivation, as an ingredient in the substrate, and assess the growth status, nutritional values, and sensory characteristics of fruiting body. The results showed that the strains could grow well on the cultivated substrate with 20% addition of TER. The total amount of hydrolyzed amino acids in the fruiting bodies of three TER-based groups (TER accounted for 10%, 20%, and 37.5%, respectively) was higher than that of the control group, and the total amount of essential amino acids was increased by 33.33%, 22.47%, and 9.92% compared with the control group, respectively. In addition, the results of gas chromatography-mass spectrometry (GC-MS) revealed that the addition of TER to the cultivation of substrate significantly enhanced the content of typical mushroom-flavor compounds in button mushroom, such as 1-octen-3-ol, 3-octanol, and 1-octen-3-one. It can be concluded that TER may be an ideal choice for the substrate in commercial cultivation of button mushroom.

Mutational Analysis of Aspergillus fumigatus Volatile Oxylipins in a Drosophila Eclosion Assay

Aspergillus fumigatus is a ubiquitous opportunistic pathogen. We have previously reported that volatile organic compounds (VOCs) produced by A. fumigatus cause delays in metamorphosis, morphological abnormalities, and death in a Drosophila melanogaster eclosion model. Here, we developed A. fumigatus deletion mutants with blocked oxylipin biosynthesis pathways (∆ppoABC) and then exposed the third instar larvae of D. melanogaster to a shared atmosphere with either A. fumigatus wild-type or oxylipin mutant cultures for 15 days. Fly larvae exposed to VOCs from wild-type A. fumigatus strains exhibited delays in metamorphosis and toxicity, while larvae exposed to VOCs from the ∆ppoABC mutant displayed fewer morphogenic delays and higher eclosion rates than the controls. In general, when fungi were pre-grown at 37 °C, the effects of the VOCs they produced were more pronounced than when they were pre-grown at 25 °C. GC-MS analysis revealed that the wild-type A. fumigatus Af293 produced more abundant VOCs at higher concentrations than the oxylipin-deficient strain Af293∆ppoABC did. The major VOCs detected from wild-type Af293 and its triple mutant included isopentyl alcohol, isobutyl alcohol, 2-methylbutanal, acetoin, and 1-octen-3-ol. Unexpectedly, compared to wild-type flies, the eclosion tests yielded far fewer differences in metamorphosis or viability when flies with immune-deficient genotypes were exposed to VOCs from either wild-type or ∆ppoABC oxylipin mutants. In particular, the toxigenic effects of Aspergillus VOCs were not observed in mutant flies deficient in the Toll (spz⁶) pathway. These data indicate that the innate immune system of Drosophila mediates the toxicity of fungal volatiles, especially via the Toll pathway.

Extraction and trapping of truffle flavoring compounds into food matrices using supercritical CO2

A supercritical fluid extraction methodology was used to extract flavoring and bioactive compounds from truffles. Some parameters such as CO₂ flow rate (1-3 mg/mL), extraction time (15-90 min) and different trapping food matrices (grape seed oil, gelatin, agar agar and water) were optimized using response surface methodology to enhance extraction and trapping yields. The optimal conditions (2.27 mg/mL CO₂ flow rate, 82.5 min when using 40 °C and 30 MPa, with 1 mL grape seed oil as trapping matrix) obtained with Tuber melanosporum were applied to three different truffle species: Terfezia claveryi, Tuber aestivum and Tuber indicum. A total of 32 metabolites were profiled in the extracts using ultra-high-performance supercritical fluid chromatography coupled to quadrupole time-of-flight mass spectrometry. Compounds such as brassicasterol ergosta-7,22-dienol, oleic and linoleic acid were found at similar amounts in all the extracts but other molecules (e.g. fungal sterols) showed a particular distribution depending on the specie studied and whether a trapping matrix was used at the SFE outlet.

Volatile Compounds Governed by Single Recessive Gene Impart Aroma in Sponge Gourd (Luffa cylindrica L. Roem)

As a vegetable crop, sponge gourd is widely consumed worldwide due to its health promoting and nutraceutical value. This study describes genetics of an aromatic genotype VRSG-7-17 and deciphers the genetic control and volatile compound composition of sponge gourd. To study the inheritance of this trait, a cross was made between aromatic light-green-fruited VRSG-7-17 and non-aromatic dark-green-fruited VRSG-194 genotypes. The F₁s were found to be non-aromatic and have a green fruit colour. Chi-square (χ²) analysis of backcross and F₂ population segregating for aroma suggested that the inheritance of aroma in VRSG-7-17 is governed by a single recessive gene in a simple Mendelian fashion. The SPME-GC/MS analysis of the volatile compounds suggested that the compounds responsible for Basmati rice-like aroma were mainly hexanal, 1-octen-3-ol, 3-octanone and limonene. The aroma persists in the cooked VRSG-7-17 fruits, that did not lose fragrance traits at high temperatures. The inheritance of fruit colour was found to be controlled by a single gene with incomplete dominance. The segregation analysis showed that the aroma and fruit colour were not linked, and they segregated independently. The findings will lead to understanding the inheritance of the aromatic compounds in the sponge gourd and may be utilised in the breeding programmes for developing improved aromatic varieties.

Process Modelling and Simulation of Key Volatile Compounds of Maillard Reaction Products Derived from Beef Tallow Residue Hydrolysate Based on Proxy Models

The hydrolysis time is directly related to the flavor of the Maillard reaction, but existing proxy models cannot simulate and model the variation curves of vital volatile components. This study developed a predictive model for modelling and simulating key volatile compounds of Maillard reaction products (MRPs) derived from beef tallow residue hydrolysate. Results showed the degree of hydrolysis increased with hydrolysis time, and the most significant improvement in the roast flavor and overall acceptance was when hydrolyzing 4 h. Based on flavor dilution value and the relative odor activity value, nine key volatile components were identified, and 2-ethyl-3,5-dimethylpyrazine with roast flavor was the highest. Compared with Polynomial Curve Fitting (PCF) and Cubic Spline Interpolation (CSI), key volatile compounds of MRPs could be better modeled and simulated by the Curve Prediction Model (CPM). All results suggested that CPM could predict the changes in key volatile components produced by MRPs.

The Biosynthesis of 1-octene-3-ol by a Multifunctional Fatty Acid Dioxygenase and Hydroperoxide Lyase in Agaricus bisporus

The biosynthetic pathway from linoleic acid to 1-octen-3-ol in Agaricus bisporus has long been established, in which linoleic acid is converted to 10-hydroperoxide (10-HPOD) by deoxygenation, and 10-HPOD is subsequently cleaved to yield 1-octene-3-ol and 10-oxodecanoic acid. However, the corresponding enzymes have not been identified and cloned. In the present study, four putative genes involved in oxylipid biosynthesis, including one lipoxygenase gene named AbLOX, two linoleate diol synthase genes named AbLDS1 and AbLDS2, and one hydroperoxide lyase gene named AbHPL were retrieved from the A. bisporus genome by a homology search and cloned and expressed prokaryotically. AbLOX, AbLDS1, and AbLDS2 all exhibited fatty acid dioxygenase activity, catalyzing the conversion of linoleic acid to generate hydroperoxide, and AbHPL showed a cleaving hydroperoxide activity, as was determined by the KI-starch method. AbLOX and AbHPL catalyzed linoleic acid to 1-octen-3-ol with an optimum temperature of 35 °C and an optimum pH of 7.2, whereas AbLDS1, AbLDS2, and AbHPL catalyzed linoleic acid without 1-octen-3-ol. Reduced AbLOX expression in antisense AbLOX transformants was correlated with a decrease in the yield of 1-octen-3-ol. AbLOX and AbHPL were highly homologous to the sesquiterpene synthase Cop4 of Coprinus cinerea and the yeast sterol C-22 desaturase, respectively. These results reveal that the enzymes for the oxidative cleavage of linoleic acid to synthesize 1-octen-3-ol in A. bisporus are the multifunctional fatty acid dioxygenase AbLOX and hydroperoxide lyase AbHPL.

Effects of Frying Conditions on Volatile Composition and Odor Characteristics of Fried Pepper (Zanthoxylum bungeanum Maxim.) Oil

Fried pepper (Zanthoxylum bungeanum Maxim.) oil (FPO) is widely used in Chinese cuisine because of its unique aroma. To investigate the effects of different frying temperatures and different frying times on the volatile composition and odor characteristics of FPOs, descriptive sensory analysis (DSA), solvent-assisted flavor evaporation–gas chromatography–mass spectrometry (SAFE–GC–MS) and electronic nose (E-nose) were used to analyze the FPOs (FPO1–FPO4 represented the pepper oil fried at 110 °C, 120 °C, 130 °C, and 140 °C; FPO5–FPO7 represented the pepper oil fried for 10 min, 20 min and 30 min). The results showed that FPO3 and FPO6 had strong citrus-like and floral aromas and exhibited significant advantages in sensory attributes. A total of 46 volatile compounds were identified by SAFE–GC–MS; among them, FPO3 and FPO6 had a higher volatile compound content. β-Caryophyllene was detected in only FPO3 and FPO6; linalool was higher in FPO3 and FPO6, which might cause them to exhibit stronger floral and citrus-like aromas. The presence of (2E,4E)-2,4-decanedienal would be one of the reasons for the strong fatty aroma exhibited in FPO4 and FPO7. FPO3 and FPO6 were associated with citrus-like and floral aromas by partial least squares regression (PLSR) analysis, which agreed with the sensory evaluation results.

Rapid Production of Fish Sauce from the Internal Organs of White Sturgeon, Acipenser transmontanus Richardson, 1836

The internal organs of white sturgeon in Miyazaki Prefecture are discarded during processing. Therefore, we tried to produce fish sauce using a short-term manufacturing method. The minced internal organs were autolyzed by endogenous proteases at 50 °C. During autolysis, the protein contents of the supernatant and precipitate after centrifugation were analyzed by the Kjeldahl method, and the protein size was monitored by SDS-PAGE. This analysis showed that the extraction rate was about 60% after treatment at 50 °C for 24 h. The major bands at 200 kDa, 43 kDa, and 40 kDa detected before the start of the treatment gradually disappeared over time. Fifteen components were detected as the main volatile components. These components increased sharply and then decreased during incubation at 50 °C for 24 h. The fish sauce produced had a good aroma after incubation at 50 °C for 72 h.

Potential of Microorganisms to Decrease the "Beany" Off-Flavor: A Review

Vegetable proteins are in high demand due to current issues surrounding meat consumption and changes in eating habits, but they are still not accepted by consumers due to their strong bitterness, astringent taste, and "beany" off-flavor. This review aimed to give an overview of the "beany" off-flavor and the potential of microorganisms to decrease it. Twenty-six volatile compounds were identified from the literature as contributing to the "beany" off-flavor, and their formation pathways were identified in a legume matrix, pea. Biotechnological ways to improve the flavor by reducing these volatile compounds were then looked over. As aldehydes and ketones are the main type of compounds directly linked to the "beany" off-flavor, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) were focused on. By converting aldehyde and ketones into alcohols or carboxylic acids, these two enzymes have the potential to decrease the off-flavor. The presence of the two enzymes in a selection of microorganisms (Lactobacillus acidophilus, Limosilactobacillus fermentum, Lactiplantibacillus plantarum, Streptococcus thermophilus, Saccharomyces cerevisiae, and Gluconobacter suboxydans) was done with a catabolism and a bioinformatical study. Finally, the correlation between the presence of the enzyme and the efficacy to improve the flavor was investigated by comparison with the literature. The presence of ADH and/or ALDH in the strain metabolism seems linked to an odor improvement. Especially, a constitutive enzyme (ADH or ALDH) in the catabolism should give better results, showing that some fermentative types are more inclined to better the flavor. Obligatory fermentative strains, with a constitutive ADH, or acetic acid bacteria, with constitutive ADH and ALDH, show the best results and should be favored to reduce the amount of compounds involved in the "beany" off-flavor and diminish that off-flavor in legume proteins.

Effects of drying temperature on umami taste and aroma profiles of mushrooms (Suillus granulatus)

Temperature is one of the most important factors for drying edible mushrooms. To evaluate the effects of different hot-air drying (HAD) temperatures on the umami taste and aroma profile of Suillus granulatus (S. granulatus) mushrooms, we measured umami substances and volatile compounds of S. granulatus dried at 40°C, 50°C, 60°C, 70°C, and 80°C. Results showed that when dried at 60°C, S. granulatus exhibited significantly higher (p < 0.05) equivalent umami concentration, taste activity values of glutamic acid (Glu) and 5'-guanosine monophosphate (5'-GMP), and electronic tongue umami sensory scores. The results identified a total of 71 volatile components of which geranylacetone, benzaldehyde, phenylethyl alcohol, and 3-methylbutanoic acid were the dominant compounds. Sensory evaluation and relative odor activity values (ROAVs) revealed that 16 volatile compounds were the key volatile organic compounds contributing mushroom-like and sweet odor to the overall aroma of S. granulatus; these included 1-octen-3-ol (ROAV: 15.11-62.06) and ethyl phenylacetate (ROAV: 13.62-79.11). The drying temperature changed the aroma profile of S. granulatus. Furthermore, the mushroom dried at 60°C had a more desirable mushroom-like and almond odor. It was, therefore, proposed that HAD at 60°C was optimal for retaining a pleasant flavor in S. granulatus. This study provides a theoretical basis for the optimal drying condition selection for the mushroom processing industry. PRACTICAL APPLICATION: Hot-air drying at 60°C can significantly retain the flavor of S. granulatus and is an optimal temperature for mushroom drying.

Evolution Analysis of Free Fatty Acids and Aroma-Active Compounds during Tallow Oxidation

To explore the role of fatty acids as flavor precursors in the flavor of oxidized tallow, the volatile flavor compounds and free fatty acid (FFAs) in the four oxidization stages of tallow were analyzed via gas chromatography (GC)-mass spectrometry (MS), the aroma characteristics of them were analyzed by GC-olfactory (GC-O) method combined with sensory analysis and partial least-squares regression (PLSR) analysis. 12 common FFAs and 35 key aroma-active compounds were obtained. Combined with the results of odor activity value (OAV) and FD factor, benzaldehyde was found to be an important component in unoxidized tallow. (E,E)-2,4-Heptadienal, (E,E)-2,4-decadienal, (E)-2-nonenal, octanal, hexanoic acid, hexanal and (E)-2-heptenal were the key compounds involved in the tallow flavor oxidation. The changes in FFAs and volatile flavor compounds during oxidation and the metabolic evolution of key aroma-active compounds are systematically summarized in this study. The paper also provides considerable guidance in oxidation control and meat flavor product development.

Bacterial type III effector-induced plant C8 volatiles elicit antibacterial immunity in heterospecific neighbouring plants via airborne signalling

Upon sensing attack by pathogens and insect herbivores, plants release complex mixtures of volatile compounds. Here, we show that the infection of lima bean (Phaseolus lunatus L.) plants with the non-host bacterial pathogen Pseudomonas syringae pv. tomato led to the production of microbe-induced plant volatiles (MIPVs). Surprisingly, the bacterial type III secretion system, which injects effector proteins directly into the plant cytosol to subvert host functions, was found to prime both intra- and inter-specific defense responses in neighbouring wild tobacco (Nicotiana benthamiana) plants. Screening of each of 16 effectors using the Pseudomonas fluorescens effector-to-host analyser revealed that an effector, HopP1, was responsible for immune activation in receiver tobacco plants. Further study demonstrated that 1-octen-3-ol, 3-octanone and 3-octanol are novel MIPVs emitted by the lima bean plant in a HopP1-dependent manner. Exposure to synthetic 1-octen-3-ol activated immunity in tobacco plants against a virulent pathogen Pseudomonas syringae pv. tabaci. Our results show for the first time that a bacterial type III effector can trigger the emission of C8 plant volatiles that mediate defense priming via plant-plant interactions. These results provide novel insights into the role of airborne chemicals in bacterial pathogen-induced inter-specific plant-plant interactions.

Effect of Microbial Fermentation on the Fishy-Odor Compounds in Kelp (Laminaria japonica)

Kelp (Laminaria japonica) is an important marine resource with low cost and rich nutrition. However, its fishy odor has compromised consumer acceptance. In this study, the effects of fermentation with Lactobacillus plantarum FSB7, Pediococcus pentosaceus CICC 21862 and Saccharomyces cerevisiae SK1.008 on fishy notes in kelp was studied using gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS) and odor activity values (OAVs). Forty-four volatile organic compounds (VOCs) were identified in unfermented kelp, most of which were aldehydes, followed by alkanes, alcohols and ketones. Among them were 19 volatile compounds with OAV greater than one. Substances containing α,β-unsaturated carbonyl structure (1-Octen-3-one, (E,Z)-2,6-nonadienal, (E,E)-2,4-decadienal, etc.) are the main contributors to kelp fishy odor. The number of VOCs in kelp samples fermented by L. plantarum, P. pentosaceus and S. cerevisiae were decreased to 22, 24 and 34, respectively. GC-IMS shows that the fingerprint of the S. cerevisiae fermented sample had the most obvious changes. The disappearance of 1-octen-3-one and a 91% decrease in unsaturated aldehydes indicate that S. cerevisiae was the most effective, while L. plantarum and P. pentosaceus only reached 43-55%. The decrease in kelp fishy notes was related to the decrease in α,β-unsaturated carbonyl groups. The experimental results show that odor reduction with fermentation is feasible.

The formation of key aroma compounds in roasted mutton during the traditional charcoal process

The formation of key aroma compounds in roasted mutton during the traditional charcoal process were investigated. The results indicated that the samples roasted for 0-15 min could be discriminated using a flash GC E-nose and GC-O-MS combined with multivariate data analysis. A total of 37 odorants were identified, among which 15 odorants were confirmed as key aroma compounds by aroma recombination experiments. Significant increases in key aroma compositions and concentrations in samples were observed during the roasting process, in which hexanal had the highest concentration. The odour activity values (OAVs) of 15 key aroma compounds were maintained at high levels in the samples after roasting for 10 min. The roasted mutton had typical aromas of meaty, fatty, roasty, grassy, and sweet odours. The multivariate linear modeling indicated that a lower specific heat capacity and lower water activity could contribute to the formation of aroma compounds of samples.

Comparison of the umami taste and aroma of dried Suillus granulatus packed using four different packaging methods

Umami and aroma are important flavor qualities of edible mushrooms, and packaging can maintain or improve the flavor during storage. This study explored the effects of light-proof packaging (LPP), light-transparent packaging (LTP), vacuum light-proof packaging (VLPP), and vacuum light-transparent packaging (VLTP) on umami taste and aroma of dried Suillus granulatus. Monosodium glutamate-like amino acid content, equivalent umami concentration, and electronic tongue umami sensory scores in VLTP were higher at 2, 4, and 6 months and higher in LTP at 8 and 10 months. Principal component analysis of aroma components showed that the comprehensive scores were higher for the transparent packaging. Ketones and pyrazines were more abundant in transparent packaging. Flavor quality was better at 4-6 months, based on the equivalent umami concentration and the concentration of eight-carbon compounds that contribute to aroma. Transparent packaging is a promising way to optimize the flavor of dried Suillus granulatus.

Transcriptome of different fruiting stages in the cultivated mushroom Cyclocybe aegerita suggests a complex regulation of fruiting and reveals enzymes putatively involved in fungal oxylipin biosynthesis

BACKGROUND

Cyclocybe aegerita (syn. Agrocybe aegerita) is a commercially cultivated mushroom. Its archetypal agaric morphology and its ability to undergo its whole life cycle under laboratory conditions makes this fungus a well-suited model for studying fruiting body (basidiome, basidiocarp) development. To elucidate the so far barely understood biosynthesis of fungal volatiles, alterations in the transcriptome during different developmental stages of C. aegerita were analyzed and combined with changes in the volatile profile during its different fruiting stages.

RESULTS

A transcriptomic study at seven points in time during fruiting body development of C. aegerita with seven mycelial and five fruiting body stages was conducted. Differential gene expression was observed for genes involved in fungal fruiting body formation showing interesting transcriptional patterns and correlations of these fruiting-related genes with the developmental stages. Combining transcriptome and volatilome data, enzymes putatively involved in the biosynthesis of C8 oxylipins in C. aegerita including lipoxygenases (LOXs), dioxygenases (DOXs), hydroperoxide lyases (HPLs), alcohol dehydrogenases (ADHs) and ene-reductases could be identified. Furthermore, we were able to localize the mycelium as the main source for sesquiterpenes predominant during sporulation in the headspace of C. aegerita cultures. In contrast, changes in the C8 profile detected in late stages of development are probably due to the activity of enzymes located in the fruiting bodies.

CONCLUSIONS

In this study, the combination of volatilome and transcriptome data of C. aegerita revealed interesting candidates both for functional genetics-based analysis of fruiting-related genes and for prospective enzyme characterization studies to further elucidate the so far barely understood biosynthesis of fungal C8 oxylipins.

Impact of post-harvest processing or thermal dehydration on physiochemical, nutritional and sensory quality of shiitake mushrooms

Shiitake mushrooms are one of the most popular and highly consumed mushrooms worldwide both in fresh and dry forms. However, it rapidly starts losing its quality immediately after harvest which necessitates processing and/or proper storage before being distributed. However, the processes used for preserving other mushrooms (e.g., Agaricus) become unviable for shiitake due to its uniqueness (higher respiration rate, varied biochemicals, growth, etc.) which demands individual studies on shiitake. This review starts by listing the factors and their interdependence leading to a quality decline in shiitake after harvest. Understanding well about these factors, numerous post-harvest operations preserve shiitake as fresh form for a shorter period and as dried forms for a longer shelf-life. These processes also affect the intrinsic quality and nutrients of shiitake. This review comprehensively summarizes and discusses the effects of chemical processing (washing, fumigation, coating, and ozone), modified atmosphere packaging (including irradiation) on the quality of fresh shiitake while discussing their efficiency in extending their shelf-life by inhibiting microbial spoilage and deterioration in quality including texture, appearance, nutrients, and favor. It also reviews the impact of thermal dehydration on the quality of dried shiitake mushrooms, especially the acquired unique textural, nutritional, and aromatic properties along with their merits and limitations. Since shiitake are preferred to be low-cost consumer products, the applicability of freeze-drying and sophisticated novel methodologies, which prove to be expensive and/or complex, are discussed. The review also outlines the challenges and proposes the subsequent future directives, which either retains/enhances the desirable quality in shiitake mushrooms.

Analysis of volatile compounds and flavor fingerprint in Jingyuan lamb of different ages using gas chromatography-ion mobility spectrometry (GC-IMS)

In this study, gas chromatography coupled to an ion mobility spectrometry (GC-IMS) was used for analyzing some volatile components and flavor fingerprint in samples from Jingyuan lambs of different ages (2, 6, and 12 months). The data obtained from ion mobility were processed using laboratory analysis view processing software for fingerprint recognition, and the principal component analysis (PCA) was performed. GC-IMS provided information on the characteristics and strength of 66 volatile flavor compounds (monomers and dimers). The differences in flavoring substances between lambs of different ages were observed. The compounds with higher intensity peaks in the lamb meat samples were alcohols (1-octen-3-ol, ethanol, (E)-2-hexen-1-ol, 1-pentanol, and 2-propanol), ketones (2-pentanone, 2-heptanone, 3-hydroxy-2-butanone, 2-hexanone, 2-butanone, 2-propanone, and 4-methyl-2-pentanone), aldehydes (n-nonanal, octanal, heptanal, 3-methylbutanal, hexanal, pentanal, 2-methylbutanal, (E)-2-octenal, (E)-2-nonenal, methional, and phenylacetaldehyde), esters (methyl benzoate), furan (2-pentylfuran), and thiazole (trimethylthiazole). The results showed that the flavor fingerprint in samples from Jingyuan lambs of different ages (2, 6, and 12 months) can be established by GC-IMS and PCA based on the identified volatile compounds. This method might be used for the rapid and comprehensive analysis of volatile components in lamb meat.

Bio-Based Cycloalkanes: The Missing Link to High-Performance Sustainable Jet Fuels

The development of sustainable energy solutions that reduce global carbon emissions, while maintaining high living standards, is one of the grand challenges of the current century. Transportation fuels are critical to economic development, globalization, and the advancement of society. Although ground vehicles and small aircraft are beginning a slow transition toward electric propulsion with energy sourced from solar radiation or wind, the extreme power requirements of jet aircraft require a more concentrated source of energy that is conveniently provided by liquid hydrocarbon fuels. This Review describes recent efforts to develop efficient routes for the conversion of crude biomass sources (e. g., lignocellulose) to cycloalkanes. These cycloalkanes impart advantageous properties to jet fuels, including increased density, higher volumetric heat of combustion, and enhanced operability. The combination of bio-based cycloalkanes and synthetic paraffinic kerosenes allows for the preparation of 100 % bio-based fuels that can outperform conventional petroleum-based fuels. In this Review methods are described that convert biomass-derived small molecules, including furfural, furfuryl alcohol, 5-hydroxymethylfurfural, cyclic ketones, phenolics, acyclic ketones, cyclic alcohols, furans, esters, and alkenes to high-density cycloalkanes. In addition to describing the chemical transformations and catalysts that have been developed to efficiently produce various cycloalkanes, this Review includes summaries of key fuel properties, which highlight the ability to generate fuels with customized performance metrics. This work is intended to inspire other researchers to study the conversion of sustainable feedstocks to full-performance aviation fuels. An acceleration of this research is critical to reducing the carbon footprint of commercial and military aviation on a timescale that will help blunt the impacts of global warming.

Biosynthesis of (R)-(-)-1-Octen-3-ol in Recombinant Saccharomyces cerevisiae with Lipoxygenase-1 and Hydroperoxide Lyase Genes from Tricholoma matsutake

Tricholoma matsutake is an ectomycorrhizal fungus, related with the host of Pinus densiflora. Most of studies on T. matsutake have focused on mycelial growth, genes and genomics, phylogenetics, symbiosis, and immune activity of this strain. T. matsutake is known for its unique fragrance in Eastern Asia. The most major component of its scent is (R)-(-)-1-octen-3-ol and is biosynthesized from the substrate linoleic acid by the sequential reaction of lipoxygenase and peroxide lyase. Here, we report for the first time the biosynthesis of (R)-(-)- 1-octen-3-ol of T. matsutake using the yeast Saccharomyces cerevisiae as a host. In this study, cDNA genes correlated with these reactions were cloned from T. matsutake, and expression studies of theses genes were carried out in the yeast Saccharomyces cerevisiae. The product of these genes expression study was carried out with Western blotting. The biosynthesis of (R)-(-)- 1-octen-3-ol of T. matsutake in recombinant Saccharomyces cerevisiae was subsequently identified with GC-MS chromatography analysis. The biosynthesis of (R)-(-)-1-octen-3-ol with S. cerevisiae represents a significant step forward.

Analysis of volatile compounds of Lentinula edodes grown in different culture substrate formulations

Volatile compounds of Lentinula edodes grown in different culture substrate (CS) formulations were analyzed to reveal (i) the relationship between volatile compound production and CS formulations, (ii) the contribution of volatile compounds to L. edodes flavor, (iii) the activities of LOX and γ-GGT enzymes, (iv) γ-GGT gene expression, and (v) the correlation between enzyme activity and volatile compound production. Our results showed that 82 kinds of volatile compounds were analyzed; 25 volatile compounds were considered key flavor components, and sulfur containing compounds, eight-carbon compounds, and aldehyde compounds also had great contributions to mushroom flavor. Bagasse could be used as a partial substitute for sawdust as a carbon source. LOX and γ-GGT activities showed a weak correlation with the volatile end products. The results indicated that the mechanisms by which CS formulations influence volatile compounds production were complex.

Comparison of Volatile and Nonvolatile Compounds in Rice Fermented by Different Lactic Acid Bacteria

The production of rice-based beverages fermented by lactic acid bacteria (LAB) can increase the consumption of rice in the form of a dairy replacement. This study investigated volatile and nonvolatile components in rice fermented by 12 different LABs. Volatile compounds of fermented rice samples were analyzed using gas chromatography-mass spectrometry (GC-MS) combined with solid-phase microextraction (SPME), while nonvolatile compounds were determined using gas chromatography-time-of-flight/mass spectrometry (GC-TOF/MS) after derivatization. The 47 identified volatile compounds included acids, aldehydes, esters, furan derivatives, ketones, alcohols, benzene and benzene derivatives, hydrocarbons, and terpenes, while the 37 identified nonvolatile components included amino acids, organic acids, and carbohydrates. The profiles of volatile and nonvolatile components generally differed significantly between obligatorily homofermentative/facultatively heterofermentative LAB and obligatorily heterofermentative LAB. The rice sample fermented by Lactobacillus sakei (RTCL16) was clearly differentiated from the other samples on principal component analysis (PCA) plots. The results of PCA revealed that the rice samples fermented by LABs could be distinguished according to microbial strains.

1-Octen-3-ol, a self-stimulating oxylipin messenger, can prime and induce defense of marine alga

BACKGROUND

Short chain oxylipins in plants as the main volatile organic carbon have been speculated to playing an important role for plant innate immunity, however, not yet intensively studied and far away established as the fully recognized algae defense signals.

RESULTS

The production of 1-octen-3-ol is self-amplified via the fatty acid-oxylipin metabolic cycle through positive feedback loop. Production of 1-octen-3-ol may act as a messenger that induces P. haitanensis to be in a "primed" state and ready for defense by upregulating the synthesis of methyl jasmonic acid, indole-3-acetic acid, and gibberellin A3. Production of these oxylipins also adjust the redox state in cells, resulting in host defense activation.

CONCLUSIONS

We provide the first demonstration that 1-octen-3-ol from P. haitanensis, can act as a self-stimulating community messenger. The multiple effects of 1-octen-3-ol may explain why P. haitanensis, a very ancient lineage within plant kingdom, thrives in the niche of intertidal zones.

Bioformation of Volatile and Nonvolatile Metabolites by Saccharomycopsis fibuligera KJJ81 Cultivated under Different Conditions-Carbon Sources and Cultivation Times

Saccharomycopsis fibuligera KJJ81 isolated from nuruk is an amylolytic yeast that is widely used as a microbial starter in various fermented foods. Volatile and nonvolatile metabolites of S. fibuligera KJJ81 were investigated according to different carbon sources and cultivation times using a nontargeted metabolomic approach. Partial-least-squares discriminant analysis was applied to determine the major metabolites, which were found to be closely related to the clustering and discrimination of S. fibuligera KJJ81 samples. Some volatile metabolites derived from phenylalanine, such as 2-phenylethanol, 2-phenylethyl acetate, and ethyl phenylacetate, were predominantly found in cultivation medium containing glucose (YPD medium). In addition, the level of 2-phenylethanol increased continuously with the cultivation time. In terms of nonvolatile metabolites, carbohydrates (mannose, arabitol, and mannitol), fatty acids (palmitic acid and stearic acid), organic acids (oxalic acid and succinic acid), and amino acids (isoleucine, serine, alanine, glutamic acid, glycine, proline, phenylalanine, and threonine) were the main contributors to S. fibuligera KJJ81 samples cultivated in YPD medium according to cultivation time. These results show that the formation of volatile and nonvolatile metabolites of S. fibuligera KJJ81 can be significantly affected by both the carbon sources and the cultivation time.

Cyclooxygenases and lipoxygenases are used by the fungus Podospora anserina to repel nematodes

Oxylipins are secondary messengers used universally in the living world for communication and defense. The paradigm is that they are produced enzymatically for the eicosanoids and non-enzymatically for the isoprostanoids. They are supposed to be degraded into volatile organic compounds (VOCs) and to participate in aroma production. Some such chemicals composed of eight carbons are also envisoned as alternatives to fossil fuels. In fungi, oxylipins have been mostly studied in Aspergilli and shown to be involved in signalling asexual versus sexual development, mycotoxin production and interaction with the host for pathogenic species. Through targeted gene deletions of genes encoding oxylipin-producing enzymes and chemical analysis of oxylipins and volatile organic compounds, we show that in the distantly-related ascomycete Podospora anserina, isoprostanoids are likely produced enzymatically. We show the disappearance in the mutants lacking lipoxygenases and cyclooxygenases of the production of 10-hydroxy-octadecadienoic acid and that of 1-octen-3-ol, a common volatile compound. Importantly, this was correlated with the inability of the mutants to repel nematodes as efficiently as the wild type. Overall, our data show that in this fungus, oxylipins are not involved in signalling development but may rather be used directly or as precursors in the production of odors against potential agressors.

SIGNIFICANCE

We analyzse the role in inter-kingdom communication of lipoxygenase (lox) and cyclooxygenase (cox) genes in the model fungus Podospora anserina. Through chemical analysis we define the oxylipins and volatile organic compounds (VOCs)produce by wild type and mutants for cox and lox genes, We show that the COX and LOX genes are required for the production of some eight carbon VOCs. We show that COX and LOX genes are involved in the production of chemicals repelling nematodes. This role is very different from the ones previously evidenced in other fungi.

Identification and Quantitation of Potent Odorants in Spearmint Oils

Potent odorants in Native spearmint, Scotch spearmint, and Macho mint oils were determined by the combined use of gas chromatography-olfactometry (GCO), gas chromatography-mass spectrometry (GC-MS), and aroma extract dilution analysis (AEDA). Of the 85 odorants detected, ( R)-(-)-carvone was the most potent odorant in all three spearmint oils. Additional predominant odorants in all spearmint oils included eugenol, ethyl ( S)-(+)-2-methylbutanoate, ( E)-β-damascenone, and (3 E,5 Z)-1,3,5-undecatriene. Forty-six compounds were quantitated using various methods, including 19 by gas chromatography with flame ionization detection (GC-FID), 20 by stable isotope dilution analysis (SIDA), and 14 by GCO dilution analysis. Concentrations were used to calculate the odor activity values (OAVs) for predominant odorants in the oils. Among the compounds quantitated, those with the highest OAVs were ( R)-(-)-carvone, 1,8-cineole, ( E, Z)-2,6-nonadienal, ( E)-β-damascenone, and (3 E,5 Z)-1,3,5-undecatriene.

Chemometric Analysis of the Volatile Compounds Generated by Aspergillus carbonarius Strains Isolated from Grapes and Dried Vine Fruits

Ochratoxin A (OTA) contamination in grape production is an important problem worldwide. Microbial volatile organic compounds (MVOCs) have been demonstrated as useful tools to identify different toxigenic strains. In this study, Aspergillus carbonarius strains were classified into two groups, moderate toxigenic strains (MT) and high toxigenic strains (HT), according to OTA-forming ability. The MVOCs were analyzed by GC-MS and the data processing was based on untargeted profiling using XCMS Online software. Orthogonal projection to latent structures discriminant analysis (OPLS-DA) was performed using extract ion chromatogram GC-MS datasets. For contrast, quantitative analysis was also performed. Results demonstrated that the performance of the OPLS-DA model of untargeted profiling was better than the quantitative method. Potential markers were successfully discovered by variable importance on projection (VIP) and t-test. (E)-2-octen-1-ol, octanal, 1-octen-3-one, styrene, limonene, methyl-2-phenylacetate and 3 unknown compounds were selected as potential markers for the MT group. Cuparene, (Z)-thujopsene, methyl octanoate and 1 unknown compound were identified as potential markers for the HT groups. Finally, the selected markers were used to construct a supported vector machine classification (SVM-C) model to check classification ability. The models showed good performance with the accuracy of cross-validation and test prediction of 87.93% and 92.00%, respectively.

Microbiological characterisation and volatiles profile of model, ex-novo, and traditional Italian white wheat sourdoughs

The interplay of sourdough microbiology and generated volatile compounds that define its sensory characteristics was studied. In order to detail the flavour generating potential of microorganisms, eight single-strain dough fermentations were studied, four of them never investigated before. Moreover, for the first time, both ex-novo and traditional wheat sourdoughs were investigated and compared to chemically acidified dough. HS-SPME-GC-MS was used to sample and analyse volatile compounds, some of which have never been detected before in sourdoughs. Alcohols, esters, carbonyl compounds, and acids mainly characterised the volatile profiles. Different sourdough microbiota resulted in different volatile profiles. PCA indicated that samples could be clustered according to their specific microbiota. Production of aroma compounds was strain-specific, confirming previous findings. This study can contribute to the management of desirable features and differentiate specialty products, as well as selecting new, suitable, sourdoughs after microbial screening.

Are Some Fungal Volatile Organic Compounds (VOCs) Mycotoxins?

Volatile organic compounds (VOCs) are carbon-compounds that easily evaporate at room temperature. Toxins are biologically produced poisons; mycotoxins are those toxins produced by microscopic fungi. All fungi emit blends of VOCs; the qualitative and quantitative composition of these volatile blends varies with the species of fungus and the environmental situation in which the fungus is grown. These fungal VOCs, produced as mixtures of alcohols, aldehydes, acids, ethers, esters, ketones, terpenes, thiols and their derivatives, are responsible for the characteristic moldy odors associated with damp indoor spaces. There is increasing experimental evidence that some of these VOCs have toxic properties. Laboratory tests in mammalian tissue culture and Drosophila melanogaster have shown that many single VOCs, as well as mixtures of VOCs emitted by growing fungi, have toxic effects. This paper describes the pros and cons of categorizing toxigenic fungal VOCs as mycotoxins, uses genomic data to expand on the definition of mycotoxin, and summarizes some of the linguistic and other conventions that can create barriers to communication between the scientists who study VOCs and those who study toxins. We propose that "volatoxin" might be a useful term to describe biogenic volatile compounds with toxigenic properties.

Changes in volatile compound composition of Antrodia camphorata during solid state fermentation

BACKGROUND

Although the volatiles present in mushrooms and fungi have been investigated by many researchers, including Antrodia camphorata in submerged fermentation, there are few data available regarding changes in volatile compounds during fermentation. Our research has revealed that solid state fermentation of A. camphorata is highly odiferous compared with submerged cultures and the odor changed with increasing culture time. Therefore the aim of this study was to investigate the changes in volatile compound composition of A. camphorata during solid state fermentation.

RESULTS

Altogether, 124 major volatile compounds were identified. The volatile compounds produced by A. camphorata during growth in solid state fermentation were quite different. Oct-1-en-3-ol, octan-3-one and methyl 2-phenylacetate were predominant in exponential growth phase production, while the dominant volatiles produced in stationary phase were octan-3-one and methyl 2-phenylacetate. In stationary phase, lactone compounds in A. camphorata, such as 5-butyloxolan-2-one, 5-heptyloxolan-2-one, 6-heptyloxan-2-one, contributed greatly to peach and fruit-like flavor. Terpene and terpene alcohol compounds, such as 1-terpineol, L-linalool, T-cadinol, (E, E)-farnesol, β-elemene, cis-α-bisabolene and α-muurolene, made different contributions to herbal fresh aroma in A. camphorata. Nineteen volatile sesquiterpenes were detected from solid state fermentation of A. camphorata. The compounds 5-n-butyl-5H-furan-2-one, β-ionone, (-)-caryophyllene oxide, aromadendrene oxide, diepi-α-cedrene epoxide, β-elemene, α-selinene, α-muurolene, azulene, germacrene D, γ-cadinene and 2-methylpyrazine have not hitherto been reported in A. camphorata.

CONCLUSION

The preliminary results suggest that the aroma-active compounds produced by A camphorata in solid state fermentation might serve as an important source of natural aroma compounds for the food and cosmetic industries or antibiotic activity compounds. The sesquiterpenes could be identified as possible taxonomic markers for A. camphorata.

A model to evaluate the cytotoxicity of the fungal volatile organic compound 1-octen-3-ol in human embryonic stem cells

Microbial growth in damp indoor environments has been correlated with risks to human health. This study was aimed to determine the cytotoxicity of 1-octen-3-ol ("mushroom alcohol"), a major fungal volatile organic compound (VOC) associated with mushroom and mold odors. Using an airborne exposure technique, human embryonic stem cells were exposed for 1 h to different concentrations (0-1,000 ppm) of racemic 1-octen-3-ol and its enantiomers, (R)-(-)-1-octen-3-ol and (S)-(+)-1-octen-3-ol. Cytotoxicity was assayed using both the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and the fluorescently tagged Calcein AM-mediated "live and dead" assay. Racemic 1-octen-3-ol and (S)-(+)-1-octen-3-ol exhibited greater cytotoxicity to the undifferentiated human cell line H1 than did (R)-(-)-1-octen-3-ol. The inhibition concentration 50 (IC(50)) values assessed by the MTS assay for racemic 1-octen-3-ol, (S)-(+)-1-octen-3-ol and (R)-(-)-1-octen-3-ol were, respectively, 109, 98, and 258 ppm. These IC(50) values were 40-80-fold lower than that of vapor phase toluene, an industrial chemical used as a positive control in this study. Our report pioneers the modeling of human embryonic stem cells as an in vitro approach to screen the potential toxicity of fungal VOCs. Human embryonic stem cells exposed to 1-octen-3-ol, and its enantiomers in the vapor phase showed more cytotoxicity than those exposed to toluene.

Olfactory cues from plants infected by powdery mildew guide foraging by a mycophagous ladybird beetle

Powdery mildews (Erysiphales) are economically important plant pathogens that attack many agricultural crops. Conventional management strategies involving fungicide application face challenges, including the evolution of resistance and concerns over impacts on non-target organisms, that call for investigation of more sustainable alternatives. Mycophagous ladybird beetles (Coleoptera: Coccinellidae) feed on powdery mildew and have considerable potential as biological control agents; however, the foraging ecology and behavior of these beetles is not well understood. Here we document the olfactory cues presented by squash plants (Cucurbita moschata) infected by powdery mildew (Podosphaera sp.) and the behavioral responses of twenty-spotted ladybird beetles (Psyllobora vigintimaculata) to these cues. Volatile analyses through gas chromatography revealed a number of volatile compounds characteristic of infected plants, including 3-octanol and its analogues 1-octen-3-ol and 3-octanone. These compounds are typical "moldy" odorants previously reported in volatiles collected from other fungi. In addition, infected plants exhibited elevated emissions of several compounds also observed in collections from healthy leaves, including linalool and benzyl alcohol, which are reported to have anti-fungal properties. In Y-tube choice assays, P. vigintimaculata beetles displayed a significant preference for the odors of infected plants compared to those of healthy plants. Moreover, beetles exhibited strong attraction to one individual compound, 1-octen-3-ol, which was the most abundant of the characteristic fungal compounds identified. These results enhance our understanding of the olfactory cues that guide foraging by mycophagous insects and may facilitate the development of integrated disease-management strategies informed by an understanding of underlying ecological mechanisms.